<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <script src="./vue.js"></script>
</head>
<style>
    .black{
        color: black
    }
.one{
    color: red;
}
.two{
    color: green;
}
.three{
    color: blue;
}
</style>
<body>
    <div id="app">
        <h1 v-bind:class="x">文字</h1>
        <select v-model="x">
            <option value="black">请选择颜色</option>
            <option value="one">红色</option>
            <option value="two">绿色</option>
            <option value="three">蓝色</option>
        </select>
    </div>
</body>
<script>
    let v = new Vue({
        el:"#app",
        data:{
            x:"black",
        },
    })


</script>
</html>